Structure determination of nitrito- and thiocyanato-copper(II) complexes: X-ray structures of [Cu(Medpt)(ONO)(H 2O)]ClO 4 ( 1), [Cu(dien)(ONO)]ClO 4 ( 2) and [Cu 2(Medpt) 2(μ N,S-NCS) 2](ClO 4) 2 ( 3) (Medpt = 3,3′-diamino- N-methyldipropylamine and dien = diethylenetriamine)

Abstract

The synthesis and characterization of the monomeric nitrite complexes [Cu(Medpt)(ONO)(H 2O)]ClO 4 ( 1) and [Cu(dien)(ONO)]ClO 4 ( 2) as well as the new dinuclear bridged thiocyanato complex [Cu 2(Medpt) 2(μ N,S-NCS) 2](ClO 4) 2 ( 3) (Medpt = 3,3′-diamino- N-methyldipropylamine and dien = diethylenetriamine) are described. In complex 1, the copper center is penta-coordinated by the three N atoms of the Medpt, an oxygen atom O(1) from nitrito group and oxygen atom O(3) of a water molecule whereas in complex 2, the penta-coordinate geometry is achieved by copper bonds to the three N atoms of the dien ligand, a short bond to oxygen O(1) and a long one to the second oxygen atom O(2) of the nitrito group. In the bridged thiocyanato complex 3, the two copper centers are linked by two thiocyanate groups in an end-to-end bonding fashion where the copper ions are penta-coordinated by three N-atoms of the Medpt ligand, one N atom from the bridging thiocyanato group and the fifth coordination site is occupied by S atom from the second bridging thiocyanate ligand. The structure consists of three crystallographically independent dinuclear [Cu 2(Medpt) 2(μ N,S-NCS) 2] 2+ cations. The coordination polyhedron around the Cu(II) ions in these complexes may be described as an axially elongated square pyramid geometry (SP). The intradimer Cu⋯Cu distance in this complex ranges from 5.429(2) to 5.516(2) Å. Variable-temperature magnetic susceptibility studies for complex 3 indicate weak antiferromagnetic coupling between the Cu 2+ centers with J = −1.8 cm −1. The IR stretching frequencies of the nitrito, ν ( NO 2 - ) and thiocyanato, ν(NCS −) groups in the 1470–1100 and 2030–2120 cm −1 regions, respectively, are discussed in relation to other related species. The visible spectra of the complexes studied in different solvents were in agreement with the assigned predominant SP stereochemistry.